#include <string.h>
#include <stdlib.h>
#include "md5.h"  
  
#define F(x,y,z) ((x & y) | (~x & z))  
#define G(x,y,z) ((x & z) | (y & ~z))  
#define H(x,y,z) (x^y^z)  
#define I(x,y,z) (y ^ (x | ~z))  
#define ROTATE_LEFT(x,n) ((x << n) | (x >> (32-n)))  
#define FF(a,b,c,d,x,s,ac) { \
    a += F(b,c,d) + x + ac; \
    a = ROTATE_LEFT(a,s); \
    a += b; \
}  
#define GG(a,b,c,d,x,s,ac) { \
    a += G(b,c,d) + x + ac; \
    a = ROTATE_LEFT(a,s); \
    a += b; \
}  
#define HH(a,b,c,d,x,s,ac) { \
    a += H(b,c,d) + x + ac; \
    a = ROTATE_LEFT(a,s); \
    a += b; \
}  
#define II(a,b,c,d,x,s,ac) { \
    a += I(b,c,d) + x + ac; \
    a = ROTATE_LEFT(a,s); \
    a += b; \
}                                              

struct MD5_CTX {  
    unsigned int count[2];  //已处理的数据的bit数
    unsigned int state[4];  //当前结果
    unsigned char buffer[64]; //用于临时存放多余的位，最后填充处理    
};  
void MD5Transform(unsigned int state[4],unsigned char block[64]);  
void MD5Encode(unsigned char *output,unsigned int *input,unsigned int len);  
void MD5Decode(unsigned int *output,unsigned char *input,unsigned int len);

//用于填充的数据，注意最长为512位(64字节)
unsigned char PADDING[]={
	0x80,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
};  
 
//创建md5基础结构
MD5_CTX *MD5_CTX_Create(void){
    MD5_CTX *md5_ctx = malloc(sizeof(MD5_CTX));
    return md5_ctx;
} 
//销毁md5基础结构
void MD5_CTX_Destroy(MD5_CTX *md5_ctx){
    free(md5_ctx);
} 
//初始化
void MD5Init(MD5_CTX *context)  {  
    context->count[0] = 0;  
    context->count[1] = 0;  
    context->state[0] = 0x67452301;  
    context->state[1] = 0xEFCDAB89;  
    context->state[2] = 0x98BADCFE;  
    context->state[3] = 0x10325476;  
}
//处理输入的数据
void MD5Update(MD5_CTX *context,unsigned char *input,unsigned int inputlen) {  
    unsigned int i = 0;
	unsigned index = 0; 
	unsigned partlen = 0;  

	//计算context中缓存的待处理字节数, count为比特数要先除以8，再除以64取余
	//就是上次剩余的字节数
    index = (context->count[0] >> 3) & 0x3F;  
	//凑成一组(64字节)数据所需要的字节数
    partlen = 64 - index;  

	//将当前数据长度累加到已处理的bit数，加之前要先乘8将字节数转换乘bit数
	//这里使用两个int型模拟长整形加法，首先加低32位
    context->count[0] += inputlen << 3;  
	//如果溢出，则高32位加1
    if(context->count[0] < (inputlen << 3))  
        context->count[1]++;  		
	//再加高32位（inputlen>>29 ==> (inputlen*8)>>32
    context->count[1] += inputlen >> 29;  
  
    if(inputlen >= partlen)  {
		//如果可以补齐，则先补齐后处理一次，再继续处理后面的数据
        memcpy(&context->buffer[index],input,partlen);  
        MD5Transform(context->state,context->buffer);  
        for(i = partlen;i+64 <= inputlen;i+=64)  
            MD5Transform(context->state,&input[i]);  
        index = 0;          
    } else  {  
        i = 0;  
    }  
	//将剩余的数据追加到缓冲取，等待后续处理
    memcpy(&context->buffer[index],&input[i],inputlen-i);  
}  
//将剩余数据填充后做最后处理
void MD5Final(MD5_CTX *context,unsigned char digest[16])  {  
    unsigned int index = 0,padlen = 0;  
    unsigned char bits[8];  
	//获取缓冲区长度
    index = (context->count[0] >> 3) & 0x3F;  
	//计算填充长度，如果按64取余后不足56，则补至56, 否则先补整64再补至56
	//64-index+56 = 120-index
    padlen = (index < 56)?(56-index):(120-index);  
	//将bit数转换为大端字节序
    MD5Encode(bits,context->count,8); 
	//填充 
    MD5Update(context,PADDING,padlen);  
	//附加长度信息，并做最后处理
    MD5Update(context,bits,8);
	//将最后的整形值转换为大端字节序列  
    MD5Encode(digest,context->state,16);  
}  
//将整形值转换成大端字节序(bit序保持不变)
void MD5Encode(unsigned char *output,unsigned int *input,unsigned int len)  
{  
    unsigned int i = 0,j = 0;  
    while(j < len)  
    {  
        output[j] = input[i] & 0xFF;    
        output[j+1] = (input[i] >> 8) & 0xFF;  
        output[j+2] = (input[i] >> 16) & 0xFF;  
        output[j+3] = (input[i] >> 24) & 0xFF;  
        i++;  
        j+=4;  
    }  
}  
//将字节串看做大端字节序数组，转换为等值的整形数组
void MD5Decode(unsigned int *output,unsigned char *input,unsigned int len)  
{  
    unsigned int i = 0,j = 0;  
    while(j < len)  
    {  
        output[i] = (input[j]) |  
            (input[j+1] << 8) |  
            (input[j+2] << 16) |  
            (input[j+3] << 24);  
        i++;  
        j+=4;   
    }  
}  

//一次性处理512位(64字节)的数据(看做大端字节序数组)
void MD5Transform(unsigned int state[4],unsigned char block[64])  
{  
    unsigned int a = state[0];  
    unsigned int b = state[1];  
    unsigned int c = state[2];  
    unsigned int d = state[3];  
    unsigned int x[64];  
    MD5Decode(x,block,64);  
    FF(a, b, c, d, x[ 0], 7, 0xd76aa478);   
    FF(d, a, b, c, x[ 1], 12, 0xe8c7b756);   
    FF(c, d, a, b, x[ 2], 17, 0x242070db);   
    FF(b, c, d, a, x[ 3], 22, 0xc1bdceee);   
    FF(a, b, c, d, x[ 4], 7, 0xf57c0faf);   
    FF(d, a, b, c, x[ 5], 12, 0x4787c62a);   
    FF(c, d, a, b, x[ 6], 17, 0xa8304613);   
    FF(b, c, d, a, x[ 7], 22, 0xfd469501);   
    FF(a, b, c, d, x[ 8], 7, 0x698098d8);   
    FF(d, a, b, c, x[ 9], 12, 0x8b44f7af);   
    FF(c, d, a, b, x[10], 17, 0xffff5bb1);   
    FF(b, c, d, a, x[11], 22, 0x895cd7be);   
    FF(a, b, c, d, x[12], 7, 0x6b901122);   
    FF(d, a, b, c, x[13], 12, 0xfd987193);   
    FF(c, d, a, b, x[14], 17, 0xa679438e);   
    FF(b, c, d, a, x[15], 22, 0x49b40821);   
  
      
    GG(a, b, c, d, x[ 1], 5, 0xf61e2562);   
    GG(d, a, b, c, x[ 6], 9, 0xc040b340);   
    GG(c, d, a, b, x[11], 14, 0x265e5a51);   
    GG(b, c, d, a, x[ 0], 20, 0xe9b6c7aa);   
    GG(a, b, c, d, x[ 5], 5, 0xd62f105d);   
    GG(d, a, b, c, x[10], 9,  0x2441453);   
    GG(c, d, a, b, x[15], 14, 0xd8a1e681);   
    GG(b, c, d, a, x[ 4], 20, 0xe7d3fbc8);   
    GG(a, b, c, d, x[ 9], 5, 0x21e1cde6);   
    GG(d, a, b, c, x[14], 9, 0xc33707d6);   
    GG(c, d, a, b, x[ 3], 14, 0xf4d50d87);   
    GG(b, c, d, a, x[ 8], 20, 0x455a14ed);   
    GG(a, b, c, d, x[13], 5, 0xa9e3e905);   
    GG(d, a, b, c, x[ 2], 9, 0xfcefa3f8);   
    GG(c, d, a, b, x[ 7], 14, 0x676f02d9);   
    GG(b, c, d, a, x[12], 20, 0x8d2a4c8a);   
  
      
    HH(a, b, c, d, x[ 5], 4, 0xfffa3942);   
    HH(d, a, b, c, x[ 8], 11, 0x8771f681);   
    HH(c, d, a, b, x[11], 16, 0x6d9d6122);   
    HH(b, c, d, a, x[14], 23, 0xfde5380c);   
    HH(a, b, c, d, x[ 1], 4, 0xa4beea44);   
    HH(d, a, b, c, x[ 4], 11, 0x4bdecfa9);   
    HH(c, d, a, b, x[ 7], 16, 0xf6bb4b60);   
    HH(b, c, d, a, x[10], 23, 0xbebfbc70);   
    HH(a, b, c, d, x[13], 4, 0x289b7ec6);   
    HH(d, a, b, c, x[ 0], 11, 0xeaa127fa);   
    HH(c, d, a, b, x[ 3], 16, 0xd4ef3085);   
    HH(b, c, d, a, x[ 6], 23,  0x4881d05);   
    HH(a, b, c, d, x[ 9], 4, 0xd9d4d039);   
    HH(d, a, b, c, x[12], 11, 0xe6db99e5);   
    HH(c, d, a, b, x[15], 16, 0x1fa27cf8);   
    HH(b, c, d, a, x[ 2], 23, 0xc4ac5665);   
  
      
    II(a, b, c, d, x[ 0], 6, 0xf4292244);   
    II(d, a, b, c, x[ 7], 10, 0x432aff97);   
    II(c, d, a, b, x[14], 15, 0xab9423a7);   
    II(b, c, d, a, x[ 5], 21, 0xfc93a039);   
    II(a, b, c, d, x[12], 6, 0x655b59c3);   
    II(d, a, b, c, x[ 3], 10, 0x8f0ccc92);   
    II(c, d, a, b, x[10], 15, 0xffeff47d);   
    II(b, c, d, a, x[ 1], 21, 0x85845dd1);   
    II(a, b, c, d, x[ 8], 6, 0x6fa87e4f);   
    II(d, a, b, c, x[15], 10, 0xfe2ce6e0);   
    II(c, d, a, b, x[ 6], 15, 0xa3014314);   
    II(b, c, d, a, x[13], 21, 0x4e0811a1);   
    II(a, b, c, d, x[ 4], 6, 0xf7537e82);   
    II(d, a, b, c, x[11], 10, 0xbd3af235);   
    II(c, d, a, b, x[ 2], 15, 0x2ad7d2bb);   
    II(b, c, d, a, x[ 9], 21, 0xeb86d391);   
    state[0] += a;  
    state[1] += b;  
    state[2] += c;  
    state[3] += d;  
} 


#ifdef MD5_TEST
#include <stdio.h>
#include "md5.h"  
  
int main(int argc, char *argv[]) {  
    MD5_CTX *md5 = MD5_CTX_Create();  
    int i;  
    unsigned char encrypt[] ="admin";//21232f297a57a5a743894a0e4a801fc3  
    unsigned char decrypt[16];      
    MD5Init(md5);           
    MD5Update(md5,encrypt,strlen((char *)encrypt));  
    MD5Final(md5,decrypt);   
    MD5_CTX_Destroy(md5);
    printf("散列前: %s\n散列后(32位): ",encrypt);  
    for(i=0;i<16;i++)  {  
        printf("%02x",decrypt[i]);
    }  
    //getchar();  
    putchar('\n');
    return 0;  
}  

#endif //MD5_TEST
